The present invention relates to an insulating-film-forming composition, a method of producing the same, a silica-based insulating film, and a method of forming the same. More particularly, the invention relates to an insulating-film-forming composition suitably used for an interlayer dielectric of a semiconductor device or the like, a method of producing the same, a silica-based insulating film, and a method of forming the same.
Silica (SiO2) films formed by a vacuum process such as a CVD process have been extensively used as an interlayer dielectric film in the manufacture of semiconductor devices and the like. In recent years, in order to form an interlayer dielectric having a more uniform thickness, a spin-on-glass (SOG) film, which is a coating-type insulating film containing a tetraalkoxysilane hydrolyzate as the major component, has also been used. Along with an increase in the degree of integration of a semiconductor device, a low-relative-dielectric-constant interlayer dielectric called an organic SOG containing a polyorganosiloxane as the major component has been developed.
However, more excellent electrical insulation between conductors has been demanded accompanying a further increase in the degree of integration and multi-layering of a semiconductor device. Therefore, an interlayer dielectric exhibiting excellent storage stability, a lower relative dielectric constant, and superior mechanical strength has been in demand.
In the manufacturing process for semiconductor devices, a chemical mechanical planarization (CMP) step for planarizing an insulating layer and a washing step are conducted. For this reason, in addition to the dielectric constant characteristics, mechanical strength and chemical resistance of a degree to resist corrosion with a chemical fluid are demanded for application to an interlayer dielectric and a protective film of semiconductor devices.
A composition containing a mixture of fine particles obtained by the condensation of an alkoxysilane in the presence of ammonia and a basic partial hydrolyzate of an alkoxysilane (JP-A-5-263045, and JP-A-5-315319) and a coating solution obtained by the condensation of a basic hydrolyzate of polyalkoxysilane in the presence of ammonia (JP-A-11-340219 and JP-A-11-340220) have been proposed as materials having a low relative dielectric constant. However, the materials obtained by these methods are not suitable for industrial manufacture because of unstable properties of the reaction products and fluctuation of film characteristics such as a relative dielectric constant, cracking resistance, mechanical strength, and adhesion.
A method for forming an insulating film with a low dielectric constant from a coating solution prepared by mixing a polycarbosilane solution and a polysiloxane solution has been proposed (JP-A-2001-127152 and JP-A-2001-345317). This method, however, has a problem in that carbosilane domains and polysiloxane domains are unevenly scattered in the coating film.
A method of using an organosilicate polymer obtained by hydrolysis-condensation of a carbon bridge-containing silane oligomer which is prepared from an organometallic silane compound has been proposed (WO 2002/98955). The material obtained by this method produces a reaction product with poor stability and cannot be stored for a long period of time. In addition, the coating exhibits poor adhesion to a substrate.
A method of forming a low-dielectric-constant insulating film by hydrolysis-condensation of a highly branched polycarbosilane (U.S. Pat. No. 6,807,041) has been proposed. However, since the method requires an aging treatment with ammonia, a trimethylsilylization treatment, curing at a high temperature of 500° C., and the like after applying the polymer to a substrate, the method is unsuitable for practical use.